let wm = new WeakMap([
	[{name:'imooc'},'immoc'],
	[{name:'lesson'},'ES6 wiki']
]);
console.log(wm);

wm = new WeakMap();
console.log(wm);
let obj={name:'imooc'};
wm.set(obj,obj.name);
console.log(wm.has(obj),wm.get(obj),wm);
wm.delete(obj);
console.log(wm.has(obj),wm.get(obj),wm);
